Virtually all organisms, from bacteria to plants to man, respond to certain types of metabolic stress by altering cellular metabolism. In Drosophila melanogaster, this response is best analyzed. We are examining the relationship of cellular biochemistry to the changes in transcription which are observed after temperature or anoxic shock. The biochemical events proceed in cytoplasmic extracts from Drosophila tissue culture cells; their effects on transcription can be analyzed by incubation of isolated salivary gland nuclei in these extracts. Fractionation of the extracts provides a means of isolating and identifying the critical aspects of cellular metabolism which figure in this response to stress.